Conventionally, in an electrical test (hereinafter, referred to as “wafer test”) which is conducted in a wafer testing process for testing a semiconductor integrated circuit, a probe card attached with at least one pair of probe pins composed of tungsten type materials is used. The probe pin is formed, for example, by working a metal wire having a diameter of 50 μm to 300 μm so as to have a needle-shape at distal end of the metal wire. When these probe pins of the probe card are contacted to the semiconductor integrated circuit with a predetermined contact pressure, an electrical conduction between circuits is confirmed to be correct. According to the wafer test, a normal function and a good operation of the respective circuits are confirmed.
As a material for constituting the above probe pin, there have been generally used metal materials that are mainly composed of tungsten type material, precious metal material, precious metal alloy material or the like. In particular, there has been widely used a doped tungsten containing a minute amount of aluminum, potassium, silicon or the like as doping agent (dopant), or there has been used a rhenium-tungsten alloy containing about 1 to 30 mass % of rhenium and having a high strength and a high hardness.
The above probe pin is composed of above various materials, and manufactured by a method comprising the steps of: cutting a metal wire having a diameter of about 70 μm to 400 μm into wire elements each having a length of about 30 mm to 100 mm; machine-working (grinding working or the like) a tip end portion of each wire elements; and conducting a bending process to a portion close to the tip end portion 2 of the probe pin 1 so that the probe pin is worked to have a predetermined shape including a bent portion 7 as shown in FIG. 5. Thus prepared probe pins are attached to a probe card (Refer to Patent Document 1).
As described above, as the bending process for forming the metal wire into a predetermined shape after the tip end portion is subjected to the grinding-work, there has been generally adopted a process in which a stress in a bending direction is applied to the metal wire or the metal wire is formed by using a metal molding die.
However, since a diameter of a body portion of the metal wire is several hundreds μm while a needle-shaped portion of the tip end portion is extremely thin which is worked to have a diameter of only several tens μm, the following problems have been posed. Namely, at the time of conducting the process of bending the metal wire, a breakage is easily occurred to the needle-shaped portion, so that a lowering of a production yield of the probe pin at the bending process is easily occurred. Further, when the probe pins assembled in the probe card are used, the breakage of the probe pin easily occurs in a short period of time, and this defect is one reason of the probe pin having a short life span. Patent Document 1: Japanese Patent Application (Laid-Open) No. 6-50987